1.0 FIELD OF THE INVENTION
2.0 BACKGROUND OF THE INVENTION
3.0 SUMMARY OF THE INVENTION
3.1 DEFINITIONS
4.0 BRIEF DESCRIPTION OF THE DRAWINGS
5.0 DETAILED DESCRIPTION OF THE INVENTION
5.1 COMPOSITIONS
5.2 METHODS OF USE OF THE COMPOSITIONS OF THE PRESENT INVENTION
6.0 EXAMPLES
6.1 ENHANCEMENT OF SKIN EXFOLIATION
6.2 COMPOSITIONS FOR USE IN THE METHODS OF THE PRESENT INVENTION
6.3 STABILIZATION COMPOSITION
6.4 PROTEOLYTIC ACTIVITY AT VARYING pH LEVELS
This invention relates to novel compositions comprising one or more of an acid protease enzyme and an acidic buffer, the acidic buffer comprising an acid and a pharmaceutically or cosmetically acceptable carrier, useful for treating or preventing abnormal skin conditions, diseases or disorders, and/or for improving the texture or appearance of the skin, and/or for enhancing epidermal exfoliation, and/or for enhancing epidermal cell renewal and to methods for the use of the compositions.
It is well founded that exfoliation of epidermal layers of human skin induces an increased rate of epidermal cell renewal (E. Phillips, 1995, U.S. Pat. No. 5,431,913; W. P. Smith, 1994, Cosmetics and Toiletries 109:41-8). The human epidermis consists of multiple layers of stratified squamous epithelial cells in a constant state of renewal. New cells are formed first in the basal layer, which is the most internal membrane of the epidermis. These cells are displaced by the production of yet newer cells and subsequently are transported to the external layer of the epidermis, the stratum corneum, where they usually are shed (exfoliated) every two to three weeks. The general health and appearance of human skin depends greatly upon the rate of this process.
Certain situations or conditions, such as aging or exposure to the environment, can disturb this normal process and can lead to a generally reduced rate of cell renewal as well as an increased degree of intercorneocyte cohesion (VanScott and Yu, 1984, J. Am. Acad. Dermatol. 11:867-79). Because the time required for a cellular layer to migrate from the basal layer to the stratum corneum increases with the subject""s age, the rate of epidermal cell renewal decreases. It has been reported that in a typical twenty year old person, the cells in the outer layers of the epidermis turn over on the average, every two weeks, while cell turnover intervals of more mature skin can be as much as twice as long. (E. Phillips, 1995, U.S. Pat. No. 5,431,913). The decrease in cell renewal rate due to aging can be exacerbated by environmental conditions such as exposure to solar radiation and other climatic conditions (K. E. Burke, 1990, Postgraduate Medicine 88(1):207-27). A decrease in the cell renewal rate increases the time cells in the outer layers of skin are exposed to environmental conditions and may lead to further and/or cumulative damage. Certain studies suggest that a decrease in epidermal cell turnover rates is associated with an increase in intercorneocyte cohesion (VanScott and Yu, 1989, Cutis 43:222-28).
The cells of the epidermal layer are held together by proteinaceous components such as hemidesmosomes, desmosomes, gap junctions, glycosaminoglycans, proteoglycans, and other components present in the skin all of which have the ability to bind to each other and to cellular components. This binding together of the epidermal cells is described as xe2x80x9cintercorneocyte cohesionxe2x80x9d, and the degree of the cohesive strength involved is affected by such factors as hydration and pH. Increased intercorneocyte cohesion results in hyperkeratinization and is characterized by thick and often dry or scaly skin caused by the retention of epidermal cells. The balance that exists between cohesion and cell turnover rates is responsible for normal rejuvenation of young skin and imbalances of these factors can result in the aged, rough, and unattractive look of mature epidermal surfaces. The search for topically active components that balance cell renewal rates and intercorneocyte cohesion is prominent in dermatological research efforts today (VanScott and Yu, 1984, J. Am. Acad. Dermatol. 11:867-79).
Recent advances in this research area have provided a number of topically active acidic compounds which show promise in this regard (Yu et al., 1978, U.S. Pat. No. 4,105,783; Yu et al., 1982, U.S. Pat. No. 4,363,815). Long term treatments with these acidic compounds result in an increased rate of epidermal cell renewal. Those acidic components known to be epidermally active, such as low molecular weight hydroxy or keto acids and esters thereof, are well documented with respect to their effectiveness as keratolytic/desquamation agents. High concentrations of these acids (e.g., salicylic and glycolic acids), as well as other acids such as trichloroacetic acid, are known for their ability to cause destruction of tissue at the site of application (W. L. Epstein, 1990, in Irritant Contact Dermatitis, Jackson and Glodner, eds., Marcel Decker, Inc., New York and Basel, pp. 127-165; Remington""s Pharmaceutical Sciences, A. Osol, ed., Sixteenth Ed., Mack Publishing, Inc., Easton, Pa., 1980). At lower concentrations, these acids have been shown to have the ability to loosen the dead cells in the keratin-rich stratum corneum and interrupt intercorneocyte cohesion thereby facilitating desquamation; this activity is called xe2x80x9ckeratolytic activityxe2x80x9d (Remington""s Pharmaceutical Sciences, A. Osol, ed., Sixteenth Ed., Mack Publishing, Inc., Easton, Pa., 1980; W. P. Smith, 1994, Cosmetics and Toiletries 109:41-8).
Most keratolytics are skin irritants, including those listed above. Although some keratolytics are promoted as being more efficient than others, a comparison of the therapeutic index of each of these acids shows little advantage of one over another. The xe2x80x9ctherapeutic indexxe2x80x9d is an accurate method of rating the efficiency of these components which takes into account the component""s keratolytic efficiency as well as the levels of irritation at a given concentration. It has been shown that even low levels of these components (greater than 4% acid concentration) cause significant skin irritation. The use of even lower levels of these components reduces irritation but generally reduces keratolytic effectiveness. Furthermore, prolonged use of the acids reduces the efficiency of cell renewal induction (W. P. Smith, 1994, Cosmetics and Toiletries 109:41-8). These shortcomings point out the need for a methodology to enhance the keratolytic effectiveness of these acids at non-irritating concentrations.
The application of proteolytic enzymes in topical therapy has been used for some time for such things as scar removal from burn wounds and as an adjunct to anti-microbial therapy (G. Rodeheaver, 1975, Am. J. Surg. 129(5):537-544). These enzymes include those generally restricted to plant sources, such as papaya (papain), fig (ficin), and pineapple (bromelain). Cosmetic formulations containing extracts from these plants and promoted as enhancing the removal of outer epidermal layers by proteolytic action have been marketed commercially. Although the substrate specificity and spectrum of activity in relation to pH suggest that the proteolytic action of these formulations should result in keratolytic activity at the outer epidermal layers, applications of proteolytic enzymes previously used in topical therapy have not been without drawbacks.
Those enzymes (e.g., papain, bromelain, and ficin) currently used in cosmetic applications generally exhibit proteolytic activity over a broad pH range of pH 3-pH 9 (Glazer and Smith, 1971, in The Enzymes, Vol. 3, P. Boyer, ed., Academic Press, New York, pp. 501-546). It is probably the broad pH range of these plant-derived enzymes that is responsible for at least some of the problems associated with prolonged skin exposure. Human epidermal systems maintain a pH gradient within the stratified layers of the skin; the outer layers have been reported to exhibit an average pH of 5.5 (W. P. Smith, 1994, Cosmetics and Toiletries 109:41-48). The pH of successive layers of the epidermis increases with depth, reaching a final pH closer to the physiological range (about pH 7.4) at the dermal layer. Because the plant-derived enzymes mentioned above remain active across this pH gradient, there is no pH control over these plant enzyme activities when they are applied to the skin.
The degree of therapeutic activity received by topical application of proteolytic enzymes has been governed by the intrinsic catalytic characteristics of those enzymes. The wide range of proteolytic activity, in relation to pH, exhibited by the proteases discussed above (pH 3-9) allows for little or no control over proteolytic activity by product. formulation (Glazer and Smith, 1971, in The Enzymes, Vol. 3, P. Boyer, ed., Academic Press, New York, pp. 501-546). The plants from which these enzymes have been obtained are known to cause irritant contact dermatitis with symptoms including itching, edema, and blistering. It has been postulated that these enzymes are the primary cause of those symptoms possibly due to excessive decreases in intercorneocyte cohesion (W. L. Epstein, 1990, in Irritant Contact Dermatitis, Jackson and Glodner, eds., Marcel Decker, Inc., New York and Basel, pp. 127-165). The enzymes currently used in cosmetic applications can exhibit substrate-dependent proteolytic activity throughout all layers of the epidermis. Uncontrolled proteolysis of epidermal proteins that serve to stabilize intercorneocyte cohesion could decrease this intercorneocyte cohesion excessively and cause subsequent irritation. Proteolytic attack at the basal layer of the epidermis, where cell renewal originates, could cause imbalances in the rate of epidermal cell renewal. Blistering and edema could be the result of uncontrolled proteolytic attack by this class of enzymes at the basal membrane. This possibility is supported by the fact that injection of these plant enzymes into the skin of mammals is known to cause edema in the skin (Morimoto et al., 1987, Ensho 7(6):563-567). This finding has been used to produce experimental edema in dermatological research. Furthermore, the symptoms of irritant contact dermatitis listed above are similar to those induced by the most effective concentrations of epidermally active acidic components currently used in topical applications. Therefore, a more controlled approach to proteolytic activity with respect to topical applications should produce a desirable result without these side effects.
Compositions containing a proteolytic enzyme, pepsin, and several acids have been reported for the dissolution of dense necrotic formations seen, for example, with third degree burns (Soviet Union Patent No. 439288, 1974). There is no indication that these compositions are useful in enhancing epidermal exfoliation or that these compositions are active only for limited time periods.
Citation or identification of any reference in the background of this application shall not be construed as an admission that such reference is available as prior art to the present invention.
The present invention provides novel pharmaceutical and/or cosmetic compositions for treating or preventing abnormal skin conditions, diseases or disorders, and/or for improving the texture or appearance of the skin, and/or for enhancing epidermal exfoliation, and/or for enhancing epidermal cell renewal. The compositions comprise one or more of an acid protease and an acidic buffer. For purposes of this invention, the acid protease is an enzyme which exhibits peptidyl hydrolase (proteolytic) activity below the average pH of the surface of the skin and is significantly inactive at a pH greater than the average pH of the surface of the skin, which is about pH 5.5 for humans (W. P. Smith, 1994, Cosmetics and Toiletries 109:41-8). For men the average pH of the surface of the skin is about pH 5.3 and for women it is about pH 6.0 (Ohman and Vahlquist, 1994, Acta Dermato-Venereol. 74(5):375-379). For purposes of this invention, the average pH of the surface of the skin which is about pH 5.5 includes, in addition to others, gender-specific variations, such that a pH of about 5.5 includes a range of about pH 5.3, the average pH of the surface of a man""s skin, up to about pH 6.0, the average pH of the surface of a woman""s skin. Preferably, at a pH greater than or equal to the average pH of the surface of the skin (approximately pH 5.3-6.0), the acid proteases useful in this invention exhibit less than about 10% of the enzymatic activity they exhibit at their respective optimal pHs below the average pH of the surface of the skin.
The acid protease can be in the apoenzyme, holoenzyme, isoenzyme, or zymogen form. The acid protease component of the composition can be present in an amount of about 0.001% to about 75.0% by weight of the final composition, preferably about 0.1% to about 50%, more preferably about 1% to about 5%. The protease(s) has a specific activity of about 1.0 to about 5,000 HUT units/mg as determined by the method, as modified, described in Food Chemicals CODEX, 3rd ed., (1981), pp. 496-497, National Academy Press, Washington, D.C., see infra, Section 5.1. Preferably the protease(s) has a specific activity of about 50 to about 3000 HUT units/mg, more preferably about 500 to about 1500 HUT units/mg.
The acidic buffer is a composition which when topically applied to the skin, temporarily lowers the pH of the surface of the skin to less than about pH 5.5 but not lower than about pH 1.0, preferably to between about pH 2.5 and about pH 4.5. The acidic buffer composition comprises at least one acid and a pharmaceutically or cosmetically acceptable carrier, vehicle or excipient. The acid component of the buffer can be an inorganic or an organic acid or mixtures thereof. The acidic buffer is susceptible to neutralization to the average pH of the surface of the skin over time by natural epidermal processes, such as perspiration. The time period required for neutralization, and subsequent inactivation of the protease, will depend on the formulation of the acidic buffer. For example, shorter time periods result if the acidic buffer contains a weak acid or a weak buffering agent to counteract the relative alkalinity of the epidermis; longer time periods result if a stronger acid is utilized or a stronger buffering agent is employed in the acidic buffer. The acid component of the acidic buffer of the composition can be an organic acid or an inorganic acid or mixtures thereof and can be present in an amount of about 0.001% to about 95.0% by weight of the final composition, preferably about 0.01% to about 25%, more preferably about 1.0% to about 5%.
Control of the time period required for the pH of the surface of the skin to return to a pH of about 5.5 after topical application of a composition of the present invention allows for control of the activity of the protease enzyme. It is through this control of proteolytic activity that the present invention overcomes the drawbacks and complications found in the prior art, such as itching, burning, blistering, etc., caused by broad pH spectrum proteolytic enzymes. The period of time it takes for the surface pH of the skin to return to about pH 5.5 is determined by a number of factors, including the type of skin condition, disease or disorder that is being treated and the sensitivity of the skin of the particular subject being treated. To avoid the drawbacks and complications found in the prior art, ideally, the period of time should not exceed about 4 hours for any individual application of a composition of the present invention, preferably the period of time is between about minutes to about 4 hours, more preferably between about minutes to about 2 hours, most preferably between about minutes to about one hour.
It is to be pointed out that the pharmaceutical compositions of the present invention are those which, when administered to the skin, render a benefit or an effect of treating or preventing an abnormal biological condition, disease, or disorder. Benefits or effects of treating or preventing such abnormal condition, disease, or disorder are the reduction in severity or disappearance of the symptoms or cause of the abnormal condition, disease, or disorder. The reduction in severity or disappearance of the abnormal condition, disease, or disorder may be either in the short-or long-term. Such abnormal biological conditions, diseases, or disorders to be treated by administering a composition of the present invention include, but are not limited to, dry skin, severe dry skin, dandruff, acne, keratoses, eczema, skin flakiness, pruritus, age spots, lentigines, melasmas, wrinkles (both coarse and fine, caused by intrinsic as well as extrinsic damage), warts, blemished skin, hyperpigmented skin, hyperkeratotic skin, inflammatory dermatoses, age-related skin changes and skin in need of cleansers, as well as the effects of skin atrophy and psoriasis.
It is to be further pointed out that the cosmetic compositions of the present invention are those which, when administered to the skin, improve the texture or appearance thereof or enhance epidermal exfoliation and/or epidermal cell renewal, without necessarily rendering a benefit or an effect of treating or preventing an abnormal biological condition, disease, or disorder. In this context, improving the texture or appearance of the skin or enhancing epidermal exfoliation and/or epidermal cell renewal is meant to encompass providing a natural-looking and/or natural-feeling coating over the skin so as to enhance the beauty and/or smoothness of the skin from its pre-treated state, or to mask unwanted symptoms of an abnormal biological condition, disease, or disorder. This can include providing a temporary moisturizing effect to the epidermis. Such abnormal biological conditions, or diseases include, but are not limited to dry skin, severe dry skin, dandruff, acne, keratoses, psoriasis, eczema, skin flakiness, pruritus, age spots, lentigines, melasmas, wrinkles (both coarse and fine, caused by intrinsic as well as extrinsic damage), warts, blemished skin, hyperpigmented skin, hyperkeratotic skin, inflammatory dermatoses, age-related skin changes and skin in need of cleansers, as well as the effects of skin atrophy, and psoriasis.
In yet another embodiment, the invention encompasses methods for treating abnormal skin conditions, diseases, or disorders including but not limited to dry skin, severe dry skin, dandruff, acne, keratoses, psoriasis, eczema, skin flakiness, pruritus, age spots, lentigines, melasmas, wrinkles (both coarse and fine, caused by intrinsic as well as extrinsic damage), warts, blemished skin, hyperpigmented skin, hyperkeratotic skin, inflammatory dermatoses, age-related skin changes and skin in need of cleansers. The method comprises topically administering to an area of a subject""s skin having the condition, disease, or disorder an effective a composition comprising an acid protease which is enzymatically active below about pH 5.5 and an acidic buffer which lowers the surface pH of the skin to below about pH 5.5 for a period of time effective for the treatment of the condition, disease, or disorder, the acidic buffer being subject to neutralization by normal epidermal processes.
In yet another embodiment, the present invention provides methods for the enhancement of epidermal exfoliation and/or epidermal cell renewal comprising topically administering to an area of a subject""s skin an effective amount of a composition comprising an acid protease which is enzymatically active below about pH 5.5 and an acidic buffer which lowers the surface pH of the skin to below about pH 5.5 for a period of time effective for enhancing epidermal exfoliation and/or epidermal cell renewal, the acidic buffer being subject to neutralization by normal epidermal processes.
In another embodiment, the invention provides methods for improving the texture or appearance of the skin comprising topically administering to an area of a subject""s skin an effective amount of a composition comprising an acid protease which is enzymatically active below about pH 5.5 and an acidic buffer which lowers the surface pH of the skin to below about pH 5.5 for a period of time effective to improve the texture or appearance of the skin, the acidic buffer being subject to neutralization by normal epidermal processes.
In a still further embodiment, the invention provides methods for regulating the effects of skin atrophy comprising administering to an area of a subject""s skin an effective amount of a composition comprising an acid protease which is enzymatically active below about pH 5.5 and an acidic buffer which lowers the surface pH of the skin to below about pH 5.5 for a period of-time effective for regulating the effects of skin atrophy, the acidic buffer being subject to neutralization by normal epidermal processes.
In a preferred embodiment for enhancing epidermal exfoliation and/or epidermal cell renewal, the composition comprises pepsin and lactic acid. In this preferred embodiment for enhancing epidermal exfoliation and/or cell renewal, the composition comprises about 1.0% by weight of pepsin having a specific activity of about 1000 HUT units/mg and about 3.0% by weight of lactic acid. In a another preferred embodiment for enhancing epidermal exfoliation and/or cell renewal, the composition comprises about 1.0% by weight of pepsin having a specific activity of about 1000 HUT units/mg and about 1.5% by weight of lactic acid. In yet another preferred embodiment the composition comprises 1.0% by weight of pepsin and 1.0% by weight phosphoric acid. In another preferred embodiment the composition comprises 1.0% by weight of pepsin and 3.0% by weight phosphoric acid.
The compositions and methods of the present invention surprisingly demonstrate pharmaceutical activity or cosmetic effects against skin disorders heretofore not achieved by acids, xcex1-hydroxycarboxylic acids, salicylic acids or broad pH spectrum proteases by themselves.
As used in the present invention the following terms are intended to encompass the following:
ACIDIC BUFFER: A composition comprising an acid and a pharmaceutically or cosmetically acceptable carrier, vehicle or excipient which when topically applied to the skin lowers the surface pH of the skin to below about pH 5.5 and is subject to neutralization by natural skin processes such that the natural skin processes, over time, return the pH of the skin""s surface to normal, which is about pH5.5. The acid component of the buffer can be either an inorganic acid or an organic acid or mixtures thereof.
ACID PROTEASE: An enzyme which exhibits peptidyl hydrolase (proteolytic) activity at a pH below the average normal pH of the skin""s surface, which is about pH 5.5, and which is significantly inactive at a pH greater than or equal to such average normal skin surface pH, i.e., less than about 10% activity at about pH 5.5 or greater as compared to peak activity at pH less than about pH 5.5. The acid protease can be in the apoenzyme, holoenzyme, isoenzyme or zymogen form.
COSMETIC: A formulation to be administered to the skin which improves the texture or appearance thereof, without necessarily rendering a benefit or an effect of treating or preventing an abnormal biological condition or a disease. Such improvement includes providing a temporary moisturizing effect to the mammalian epidermis.
EFFECTIVE AMOUNT:
An amount of composition sufficient to significantly induce a positive modification in the condition to be treated, but low enough to avoid serious side effects. The effective amount of the composition will vary with the particular condition being treated, the age and physical condition of the subject being treated, the severity of the condition, the duration of the treatment, the nature of concurrent therapy, the specific composition employed, the particular pharmaceutically-acceptable carrier or cosmetically-acceptable carrier utilized, and similar factors within the knowledge and expertise of those skilled in the art.
EPIDERMAL CELL RENEWAL:
The process by which new skin cells are formed in the basal layer, are transported to the external layer, the stratum corneum, and subsequently are exfoliated and replaced by yet newer skin cells.
EXFOLIATION:
The detachment and shedding of superficial cells of an epithelium or from any tissue surface.
PHARMACEUTICAL:
A formulation to be administered to the skin which renders a benefit or an effect of treating or preventing an abnormal biological condition or a disease.
REGULATING SKIN ATROPHY:
The preventing, retarding, arresting, treating, or reversing the process of atrophy in mammalian skin.
SKIN ATROPHY: The thinning and/or general degradation of the dermis layer of mammalian skin often characterized by a decrease in collagen and/or elastin as well as decreased number, size and doubling potential of fibroblast cells. Skin atrophy is a natural result of aging, but may be caused by either intrinsic or extrinsic factors such as natural chronoaging, photodamage, burns or chemical damage, or by exposure to pollutants or allergens, e.g., cigarette smoke. Skin atrophy is often an undesirable side effect resulting from treatment with xcex1-hydroxycarboxylic acids or salicylic acids.
The present invention may be understood more fully by reference to the detailed description and illustrative examples which are intended to exemplify non-limiting embodiment e invention.